• Steel and Composite Structures
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• 제27권2호
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• pp.135-147
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• 2018

Quasi-static three-point bending tests on sandwich beams with expanded metal sheets as core were conducted. Relationships between the force and displacement at the mid-span of the sandwich beams were obtained from the experiments. Numerical simulations were carried out using ABAQUS/EXPLCIT and the results were thoroughly compared with the experimental results. A parametric analysis was performed using a Box-Behnken design (BBD) for the design of experiments (DOE) techniques and a finite element modeling. Then, the influence of the core layers number, size of the cell and, thickness of the substrates was investigated. The results showed that the increase in the size of the expanded metal cell in a reasonable range was required to improve the performance of the structure under bending collapse. It was found that core layers number and size of the cell was key factors governing the quasi-static response of the sandwich beams with lattice cores.

• Interaction and multiscale mechanics
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• 제4권2호
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• pp.155-164
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• 2011

The lattice strain evolution within polycrystalline solids is influenced by the crystal orientation and grain interaction. For multi-phase polycrystals, due to potential large differences in properties of each phase, lattice strains are even more strongly influenced by grain interaction compared with single phase polycrystals. In this research, the effects of the grain interaction and crystal orientation on the lattice strain evolution in a two-phase polycrystals are investigated. Duplex steel of austenite and ferrite phases with equal volume fraction is selected for the analysis, of which grain arrangement sensitivity is confirmed in the literature through both experiment and simulation (Hedstr$\ddot{o}$m et al. 2010). Analysis on the grain interaction is performed using the results obtained from the finite element calculation based on the model of restricted slip within crystallographic planes. The dependence of lattice strain on grain interactions as well as crystal orientation is confirmed and motivated the need for more in-depth analysis.

• Structural Engineering and Mechanics
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• 제45권5호
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• pp.703-722
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• 2013

In this paper a study about concrete arch bridges built by lattice cantilevers is presented. Lattice cantilevers are partial structures composed of deck, arch, piers and provisional steel diagonals, organized as reticular cantilever girders, in order to build arch bridges without the use of centrings, supports or temporary towers. Characteristics of this construction methodology with its variants are explained together with their implications in the erection sequence. Partial elastic scheme method is implemented in order to find initial forces of temporary cables and a forward analysis is carried out to follow the actual sequence of construction, by extending a procedure already applied to concrete cable-stayed bridges and to arches built by the classical suspended cantilever method. A numerical application on a case-study of a concrete arch bridge is performed together with a comparison between different methodologies followed for its construction sequence. Differences between erection by lattice cantilevers and cable-stayed cantilevers, are discussed. Results can be useful for designers in conceptual design of concrete arch bridges.

• 한국터널지하공간학회 논문집
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• 제18권5호
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• pp.431-439
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• 2016

본 논문은 비파괴 기법을 활용한 격자지보재의 품질평가 기법에 대한 내용을 다루었다. 일반적인 격자지보재의 성능평가는 강재의 인장강도시험과 육안조사로 이루어진다. 강재의 인장강도시험은 현장에 반입되는 격자지보의 시편을 확보하여 수행하게 되는데 이때 시편 확보를 위해 격자지보재를 훼손시켜야하는 단점을 가지고 있고 대부분의 현장에서는 인장강도시험기를 보유하고 있지 않아 시험인증기관에 의뢰해야하는 불편함을 가지고 있다. 또한 강재 생산시 발행된 성적서(Mile sheet)로 대체하기도 하나 이는 신뢰성이 결여될 수 밖에 없다. 더욱이 현장에서의 육안조사는 신뢰성이 결여되는 문제점을 가지고 있기 때문에 현장에서 자재의 훼손없이, 쉽고 빠르게 격자지보재의 품질을 평가할 수 있는 방법이 필요하게 되었다. 따라서 본 연구에서는 동일 시편에 대한 인장강도시험의 항복강도와 계장화압입시험의 항복강도를 비교 분석하여 비파괴시험법의 적용성을 분석하였다. 시험결과 계장 화압입시험은 95%이상의 정밀도를 보였으며 현장에서 성능평가가 가능한 계장화압입시험에 의한 품질평가기법을 제안하고자 한다.

• Steel and Composite Structures
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• 제52권1호
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• pp.89-107
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• 2024

This article focuses on the static and dynamic analysis and optimization of an anisogrid lattice plate subjected to axial compressive load with simply supported boundary conditions. The lattice plate includes diagonal and transverse ribs and is modeled as an orthotropic plate with effective stiffness properties. The study employs the first-order shear deformation theory and the Ritz method with a Legendre approximation function. In the realm of optimization, the Non-dominated Sorting Genetic Algorithm-II is utilized as an evolutionary multi-objective algorithm to optimize. The research findings are validated through finite element analysis. Notably, this study addresses the less-explored areas of optimizing the geometric parameters of the plate by maximizing the buckling load and natural frequency while minimizing mass. Furthermore, this study attempts to fill the gap related to the analysis of the post-buckling behavior of lattice plates, which has been conspicuously overlooked in previous research. This has been accomplished by conducting nonlinear analyses and scrutinizing post-buckling diagrams of this type of lattice structure. The efficacy of the continuous methods for analyzing the natural frequency, buckling, and post-buckling of these lattice plates demonstrates that while a degree of accuracy is compromised, it provides a significant amount of computational efficiency.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2000년도 특별강연 및 추계학술발표대회 개요집
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• pp.34-36
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• 2000

It is difficult to realize automation of welding of lattice type in shipbuilding and assembly processing of shipbuilding and steel structures. Usually, the welding parts of lattice type are welded manually. So there are limitations in continuous and stable quality controls and in increase in productivity because the welding quality depends on worker's skill. That is, automation in welding is necessary. This paper shows shows the development results of a moblie robot for welding of lattice type. Specially. algorithms for its mobile speed and seam tracking controls are introduced.

• 열처리공학회지
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• 제34권1호
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• pp.1-9
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• 2021

The martensitic stainless steel has excellent corrosion resistance and higher strength by quenching and tempering heat treatment. It has been widely used as blade material due to these properties. The hardness and impact toughness of martensitic stainless steel depended strongly on tempering temperatures. The 12Cr martensite stainless steel (SS 410) tempered about 540℃ showed temper embrittlement. To know cause of temper embrittlement in terms of phase identification, a detailed analysis of electron diffraction patterns during TEM observations has been carried out on the <110>α-Fe and <113>α-Fe zone axes for temper embrittlement specimen. The double electron diffraction spots at 1/3(211) and 2/3(211) positions were observed. The lattice space between individual diffraction spots was about 3.5 Å and this value coincide with three times to α-bcc lattice space (1.17 Å). The area which found double diffraction spots was judged metastable "zone" similar to the omega phase and induced embrittlement of SS410 material.

• 토지주택연구
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• 제2권2호
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• pp.183-188
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• 2011

최근 건설되는 터널의 심도가 깊어져 난공사 구간이 증가되며, 초장대 터널의 증가로 터널 기술 개발이 필요해지고 있다. 터널의 기술개발의 하나로 터널 강지보재로 사용되는 높이 95mm 격자지보재에 사용되는 스파이더를 최적화하여 U자형과 보강재스파이더를 개발하였다. 개발된 격자지보재의 하중지지력을 평가하기 위하여 국내에서 사용되는 4절점 휨강도 실험을 실시하였으며 실내 실험을 위해 기존 격자지보재와 개발된 격자지보재의 시편을 직선으로 제작하여 실시하였다. 실험 결과 새로운 격자지보재는 기존의 격자지보재에 비하여 하중지지력이 높게 나타났다. 지지력 평가에 의한 시편의 응력-변형 거동을 분석한 결과 기존 격자지보재는 탄소성 거동이 나타났고, 새 격자지보재는 응력연화의 거동이 나타났다. 새 격자지보재는 하중이 가해지는 지점의 위치에 따라 지지력 거동이 달라짐을 알 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제16권1호
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• pp.89-98
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• 2012

일체형 삼각 트러스 형태의 철선을 아연도금 강판에 용접한 철선일체형 데크 플레이트는 슬래브 시공 시 현장시공 최소 및 동바리와 지보공 등 거푸집 공사비 절감을 목적으로 개발되어 이미 많은 현장에 적용되고 있다. 본 연구에서는 180mm 두께 슬래브에 적용 가능한 철선일체형 데크 플레이트 시스템을 개발하기 위해 실험적 연구를 수행하였다. 상부철선, 하부철선, 래티스 철선, 경간, 단부가공방법을 변수로 채택하여 총 14개의 시험체를 실물크기로 제작하여 실험을 수행하였다. 실험결과 시험체의 최종 파괴형태 변화 및 단부가공방법이 시험체의 구조 성능에 영향을 미치지 않는 것으로 나타났으며, 하부철선의 영향보다는 래티스 철선이 시험체의 거동에 큰 영향을 미치는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제69권5호
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• pp.567-577
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• 2019

Guyed steel lattice towers (or guyed masts) are widely used for supporting antennas for telecommunications and broadcasting. This paper presents a numerical study on the static and dynamic response of guyed towers. Three-dimensional nonlinear finite-element models are used to simulate the response. Through performing static pushover analyses and free-vibration (modal) analyses, the effect of different bracing configurations is investigated. In addition, seismic analyses are performed on towers of different heights to study the influence of earthquake excitation time-lag (or the earthquake travel distance between tower anchors) and antenna weight on the seismic response of guyed towers. The results show that the inclusion of time lag in the seismic analysis of guyed towers can influence shear and moment distribution along the height of the mast. Moreover, it is found that the lateral response is insensitive to bracing configurations. The results also show that, depending on the mast height, an increased antenna weight can reduce the tower maximum base shear while other response quantities, such as cables tension force are found to be insensitive to variation in the antenna weight.